Ignition coil problems again

PangaMan · 01-25-2012, 08:31 PM

What would make the ignition coil get so hot it cuts the jeep off?? It takes about 30 minutes of driving around to get hot and cut off. Once it cools it will sart back up and will run till it cuts off again.

**SlikRic** · 01-25-2012, 08:45 PM

Just replace it, if it's getting hot and cutting out, it will SOON leave you dead in the water. Not positive of all the internal workings, but I do know it will die completely.

BagusJeep · 01-25-2012, 08:51 PM

Heat is a natural by product of that electrical field growing and falling and all coils will heat up.

However when it has reached the end of its useful life the heat will cause the internal bits to move around, which will show up as an open circuit. When it cools down it all makes contact again.

Time for a new coil. there are several options out there and Jeephammer has posted some junkyard alternates that will perform a lot better than the old one ever did.

PangaMan · 01-25-2012, 09:12 PM

It was just replaced last week. With a new accell coil

BagusJeep · 01-25-2012, 09:17 PM

In which case what voltage do you have at the connections and what was the replacement coil designed for? CJs run on 6-7V at the coil in 'run" IF the ballast resistor is in place. If someone took it out the coil would overheat if designed to be part of a ballasted ignition.

The test procedure with a test light is to connect between the disconnected +ve wire and the -ve on the battery. A bright light should appear in 'start" and a much dimmer light in "Run".

PangaMan · 01-26-2012, 06:51 AM

Ok, on the + side of the coil I have 14v on the - side I have 9.6-10 volts.

waterdowg · 01-26-2012, 07:26 AM

Why did you replace the other one? Did it have the same symtoms? How do you have it mounted?

PangaMan · 01-26-2012, 07:52 AM

the last one blew the post out of the top and shot oil everywhere. Left the key in the run position...

Ive only had the jeep since the end of January so im slowly learning all the wiring demons it has!

My question is I do not see a Balast resistor anywhere and the voltage confirms there is not one while it is running. What OHM resistor should I use and what should the voltage drop be while the engine is running. + side voltage and - side voltage?

thanks

waterdowg · 01-26-2012, 08:00 AM

Hmm I wonder if the ICM went bad as well since you left the key one. I know th ICM cam melt if the key is left on. So perhaps that is shorting and causing your problem. I really don't know for sure. Perhaps someone that knows more on ignitions will chime in.

PangaMan · 01-26-2012, 08:45 AM

Replaced that also...

**JeepHammer** · 01-26-2012, 08:47 AM

Burning coils up is usually a faulty engine 'Ground' connection.

To answer some questions,
1. The 'Ignition Resistor' in your vehicle is a 'Resistor Wire' in the harness.

The power wire for the ignition comes through the fire wall, then hits a 'Splice',
That splice splits the power in three directions,
First to the module, full battery voltage.
Second is a smaller wire to the alternator 'Excite' circuit which will have a 10 to 15 Ohm resistor wire in that line to the Excite terminal on the alternator.
The third wire out of that splice will be a 'Resistor Wire' to the ignition coil positive.

2. A cooked module will shorten the 'Dwell Time' to the point of overheating the ignition coil.
I'm sure you don't have a Dwell Meter to check the module, but a dwell meter is a way to check the ignition timing.

3. Insufficient 'Ground' to the engine block/spark plugs will cook a coil pretty quickly.
Since the coil can't discharge properly at the plugs, it winds up discharging internally.

'Super-Duper' coils are even more susceptible since they build higher voltage levels, and voltage is what breaks down internal insulation, and the makers of the 'Super Duper' coils sacrifice internal insulation for more windings to produce that extra voltage...

4. You can't test for 'Voltage' without loading the resistor in the supply line to the coil.
If you hook a small light bulb up in the circuit, then test for voltage with a load on the line, then you can get an accurate voltage drop across the resistor.

You would be better off turning the ignition switch off, setting your multi-meter to 'Ohms', unplugging the two wire connector at the alternator,
Testing the 'Harness' side of the module 'Red' wire and the unplugged coil 'Red' wire.
This will give your multi-meter a direct path through the resistor wire and will give you a direct reading of the ignition resistor.

Should read 1.35 Ohms or greater.

5. You might also do an Ohm (resistance) check between the primary (small) terminals on the coil.
I'm sure you will find your 'Super-Duper' coil is NOT making the proper resistance to work with your module.

rhfootball · 05-27-2013, 10:01 PM

Been having the same problems with my Jeep. Trying to get engine to start up, but keep having to break periodically due to the heated coil.

LumpyGrits · 05-27-2013, 10:07 PM

Key word here--------GROUND
Engine to frame to body to battery

Confirm with a volt/ohm meter.
Use heavy stranded wire that will carry the amps when needed.
LG

BagusJeep · 05-27-2013, 10:19 PM

Maybe, maybe not. If you look back at Pangaman it was unlikely he had the ballast resistor in line and had damaged the ignition module and coil in the process.

First check should be on whether the coil is wired up properly with a ballast resistor.

If the coil is toast it will stop working when hot. Time for a new one but also an electrical check over the whole system.